/*
 * Solution Template for Subbookkeeper
 * 
 * Australian Informatics Olympiad 2024
 * 
 * This file is provided to assist with reading of input and writing of output
 * for the problem. You may modify this file however you wish, or
 * you may choose not to use this file at all.
 */

#include <cstdio>

/* N is the number of letters in the word. */
int N;

/* word is the word with one missing letter */
char word[200005];

int answer;
int main(void) {
    /* Read the value of N and the word. */
    scanf("%d", &N);
    scanf("%s", word);

    /*
     * TODO: This is where you should compute your solution. Store the largest
     * score that Rebecca can achieve into the variable answer.
     */

    /* Write the answer. */
    printf("%d\n", answer);

    return 0;
}